yes it is an exact science. You must read the manufacturer's suggestions on tube pressure. If you have a thin leading edge, you will need more pressure in the kite (8 psi), while a fat leading edge can tolerate less pressure (6 psi). cold or warm, wet or dry, it doesn't matter, inflate to the recommended specifications for your kite. An underinflated kite will taco, flip inside out, fail to relaunch. An overinflated kite will perform fine but of course you really aren't supposed to overinflate it but if you are not sure if you have enough, pump it another 5 times. someone who is experienced kiteboarding will be able to put their kite to the proper pressure within about 1/2 a psi, it's like being able to read the wind speed, you get good at it, and soon will not need a pressure gauge. I don't use the "ping" test, I just grab the leading edge and press with my hands. If it is softer than vollleyball I keep pumping. It should feel a bit harder than a basketball. Use a gauge until it breaks (they all break). At that time you should know your kite well enough to inflate properly without it. If you can overinflate the struts do it, but multi pump systems are notoriously difficult to get all the struts at the same pressure, I don't try too hard to get the struts exactly right on multipump. On a one pump system inflate to the manufacturer's recommended psi.

I inflate until I am unable to bend the leading edge with my hand as my test for correct inflation. My theory is when I crash the kite in the waves it must not be possible for the waves to bend the LE enough to create a balloon animal.

General opinion is that gauges aren't accurate but they are good for ensuring consistency.

Trial and error is one option, ideally try to use lowest pressure possible to maintain correct flying and relaunch characteristics of kite to reduce stress on stitching etc too hard can damage kite or encourage it to blow when stressed. Eg if you find it's too floppy or doesn't hold it's shape pump it harder next time

If its a really windy day you may find that you need to pump your kite harder than normal to help it cope with gusts/high winds.

All kites are different.

My way is to pump it up and bend the leading edge against the sand, if it pops back into shape then its spot on. If it doesn't not enough, if its hard to bend then too much

JGTR wrote:General opinion is that gauges aren't accurate but they are good for ensuring consistency.

Trial and error is one option, ideally try to use lowest pressure possible to maintain correct flying and relaunch characteristics of kite to reduce stress on stitching etc too hard can damage kite or encourage it to blow when stressed. Eg if you find it's too floppy or doesn't hold it's shape pump it harder next time

If its a really windy day you may find that you need to pump your kite harder than normal to help it cope with gusts/high winds.

All kites are different.

My way is to pump it up and bend the leading edge against the sand, if it pops back into shape then its spot on. If it doesn't not enough, if its hard to bend then too much

10.5PSI here. That's the recommended pressure by the kite company. If I pump up less pressure, the kite struts bend and also the kite flatters in the air.The downside is that the kite is now the fourth time in the last weeks at the kite repair center because of valve leakages (valves and the connections to the struts). That sucks because every time I went out, I had to come back after 30 minutes or so and did not have a kite for the next 3 days while they repaired it. I told them to remove and re-glue the other original connections as well so hopefully that will not happen again in the near future.I have an electric pump with an accurate automatic switch-off system.

In my experience the main reason for such high pressure is bad kite and/or bridle design! Kites should be able to maintain their shape through the full range of wind and AoA without having to be pumped up to the max.

Although the 100% depower myth encourages people to fly kites in winds that they are not designed for or suitable for and pumping up to a high pressure can help stop kites deforming.